Chain for rotary kilns



c. F. FEISER, JR 3,281,134

CHAIN FOR ROTARY KILNS Filed Feb. 27, 1964 United States Patent 3,281,134 CHAIN FOR ROTARY KILNS Charles F. Feiser, Jr., York, Pa., assignor to Campbell Chain Company, York, Pa., a corporation of Pennsylvania Filed Feb. 27, 1964, Ser. No. 347,883 15 Claims. (Cl. 263-33) This invention pertains to a special form of chain and, more particularly, to a chain composed of links affording improved benefits when used in rotary kilns.

Rotary kilns having the interiors thereof heated by various means have been employed for many years in the production of various types of products, among the more common of which are cement, lime, treating powdered coal, and in general, the production of many forms of dry powdered material from either wet mixtures or slurries thereof. In general, the wet raw material, either in the form of a readily flowable slurry or a wet tumbling mass thereof is introduced at one end of 'a tubular kiln which is rotated about its axis, usually at a slight incline downwardly from the feed end toward the delivery end, while heat in the form of various types of heated gases is introduced near the lower, delivery end of the kiln for movement toward the opposite end thereof. Such heat transforms the wet slur-ry or powdered masses of wet material into a dry powdered condition.

In using kilns of this type, supplemental or auxiliary heat transfer means long have been employed in the nature of certain lengths of chains being connected at the opposite ends thereof to spaced locations on the interior of the kiln shell, the chains usually hanging in the forms of catenaries. Frequently, the chains are hung in rather close relationship to each other so as to provide engagement therebetween to assist in the chains clearing themselves of product materials adhering thereto. The purpose of the chains is to become heated by the heated gases passing through the kiln for example. As the catenaries of the chains dip into the slurry or powdered wet masses of the raw material introduced into the kilns, said material adheres to the heated surfaces of the chains and heat transferred therefrom to the material assists in drying the material, whereby the material adheres to the chains to various degrees before being knocked from contact therewith as the material progressively moves through the kiln to the exit end thereof.

For many years, conventional elliptical link-type chain has been employed in kilns for the purposes described hereinabove. There is an inherent characteristic of such chains however as far as minimizing wear is concerned and that is that the points of contact between connected links remain localized and also prevent a maximum amount of rotation of the links with respect to each other, especially for purposes of rendering them self-clearing of material adhering thereto. This difficulty was recognized in Patent No. 2,001,227, in the name of Vogel-Jorgensen, dated May 14, 1935 and the improvement afforded by said patent comprises the use of circular links or rings in the chains used for kilns whereby rotation of the rings or links about the axes thereof is possible not only to extend the life of the links by not localizing the points of contact between connected links but also render the same more readily self-clearing of adhering material.

More recently, especially to provide greater heat transfer surfaces on the chains used in kilns, the practice of using links of a generally circular nature but having the ends of the links overlapping for a certain portion of the circumference thereof, 'as distinguished from butt-welded links for example, has become popular. The laterally extending terminal surfaces of the overlapping ends of the links however afford obstructions which considerably minimize the ability of the links to slowly revolve about their axes incident to gyrating and tumbling Within the kiln, whereby maximum efliciency in effecting self-clearing of the links is not achieved, nor is localized engagement between adjacent connected links minimized. Further, although links of this type afford greater heat transfer area per link than butt-welded circular links for example, the weight of the chain, per unit length, is increased as compared with conventional butt-welded link-type chain of comparable link size, whereby additional power is required to rotate the kiln as compared with that required by kilns employing conventional chain.

It is the principal object of the present invention to provide a novel type of kiln chain formed from similar links which, in their preferred form, are circular within the plane of the links so as to permit gradual rotation of the links about the axes thereof and thereby aid in the selfcleaning function which is highly desirable in chains of this type and, more particularly, to deform the cross-sectional shape of the links, preferably throughout the lengths thereof in such manner that the exterior heat-exchanging surfaces of the links is at least equal to and preferably greater than that of links formed from conventional cylindrical wire or rod stock of comparable size which have greater weight than comparable lengths of chain embodying the invention.

Another object of the invention is to minimize wear between adjacent, connected links by not only eliminating localized contact which is inherent to elliptical link chain but also provide enhanced self-cleaning characteristics by shaping the inner surfaces of the links so as to be arcuate upon a radius which preferably is substantially equal to but not greater than one-half the inner diameter of the circular links to provide greater contact area between adjacent links than between conventional links.

Still another advantage which is ancillary to the immediate foregoing advantage is that the inner arcuate surfaces of the links preferably are wider in a direction transverse to the planes of the links than the radial thickness of the links.

A further object of the invention is to decrease the weight of the links without appreciably decreasing the outer, heat-transferring surfaces of the links by utilizing annular concave configurations on the outer surface portions of the links, the cross-sectional shapes of the links preferably being uniform throughout the entire length of the links.

A still further object of the invention somewhat ancillary to the object described immediately above is to provide each link with a cross-sectional shape which generally is somewhat triangular and the base of the triangle comprises the inner surface of the link. Still further, in the preferred embodiment, the height of the triangle is less than the width of the base thereof comprising said inner surface of the links and all corners of the triangular configuration preferably are rounded.

Still another object of the invention is to provide links having maximum heat-transfer surfaces with minimum weight commensurate with ability to resist distortion while functioning for the intended purposes of the links within a kiln, this objective being achieved by providing links which can be considered composed of circular bands of greater axial dimension than thickness and said bands being reinforced to resist deformation from their preferably circular configuration by the use of an annular rib on each link extending outward therefrom and integrally connected to said circular band. Ancillary to this object, in the preferred embodiment of the invention, said rib has a height with respect to the exterior of the band less than the width or thickness of the rib and the overall radial dimension of the links through the rib is less than the width of the links in axial direction.

Details of the foregoing objects and of the invention, as

well as other objects thereof, are set forth in the following specification and illustrated in the accompanying drawing comprising a part thereof.

In the drawing:

FIG. 1 is a fragmentary side elevational view of an exemplary kiln in which chains of the type to which the present invention pertains are employed, a portion of the shell of the mill being broken away to expose an exemplary arrangement of chains, somewhat s mplified, to render the illustration more understandable.

FIG. 2 is an enlarged transverse sectional view of the kiln shown in FIG. 1 as seen on the line 22 of said figure.

FIG. 3 is a plan view of an exemplary link embodying the principles of the present invention.

FIG. 4 is a transverse sectional view of the link shown in FIG. 3 as seen on the line 44 of said figure.

FIG. 5 is a fragmentary, partially sectional view of the coengaging portions of two links embodying the present invention and illustrating the advantageous extent of surface contact between the links.

FIG. 6 is a fragmentary cross-sectional view taken on the line 66 of FIG. 5.

FIG. 7 is an elevation of a short length of chain formed from links embodying the invention to illustrate the relative proportion of the links to each other in chain form.

FIG. 8 is a transverse cross-sectional view of the links shown in FIGS. 3 through 7, said illustration being substantially full scale of one preferred size of link.

Kilns of the type in which chains embodying the present invention are used frequently are quite large both in diameter and length. The exemplary, fragmentarily illustrated portion of kiln 10 shown in FIG. 1 may, for example, be of the order of 10 or 14 feet in diameter and as much as several hundred feet in length. However, these dimensions are merely given by way of illustration and not restriction. Not only to reinforce the shell of the kiln but also to provide appropriate anchoring means for the chains, such kilns preferably include a series of evenly spaced, radially extending plate-like ribs 12 which are secured by welding or otherwise to the inner surfaces of the shell of the kiln 10. As indicated above, kilns of the type illustrated are supported in suitable cradle arrangements, not shown, employing anti-friction rollers. The axis of the kiln usually slopes from one end to the other of the mounting means for the kiln, in accordance with the requirements of the product being produced. Raw material to be treated is fed at one end of the kiln and heat used in the drying, calcining, or other processes conducted within the kiln are introduced at the opposite end thereof. Appropriate power means, not shown, rotate the kiln, usually at a rather slow rate.

Sections of chain 14, which are diagrammatically illustrated in FIGS. 1 and 2, usually are of similar length and the opposite ends thereof are secured to the anchoring means 12 by appropriate coupling means such as clevises and bolts which extend through suitable holes in the anchoring ribs 12. As shown in exemplary manner, somewhat simplified in FIG. 1, one end of each chain is connected to a certain rib 12, and the other end of the chain is connected at a predetermined location on another rib spaced longitudinally from the first rib, whereby it is possible to effect a somewhat spiral configuration of catenaries of chains 14. If the spiral configuration is selected suitably with respect to the direction of rotation of the kiln, somewhat of a screw-feeding action may be made to take place so as to aid in advancing the material from the entrance to the exit end of the kiln. For purposes of simplifying the illustration, the arrangement of chains shown in FIG. 2 for example, has been selected to show only a single rib 12 and all of the chains connected at one end thereto. It can be visualized that such a sectional view, if illustrating all of the chains seen, for example, from one end of the kiln, only a substantially indistinguishable conglomeration of lines would be shown. Also, in this same regard, in FIG. 1, the exemplary chains 14 shown in the portion of the shell which has been broken away substantially only show a single longitudinally extending row of chains which have been connected at one end to the same approximate location 5 on successive ribs 12, while the opposite ends of the chains have been shown connected to a different, longitudinally spaced location along a similar longitudinal line of locations on successive ribs 12, so as to simplify the view.

It also should be understood with respect to FIGS. 1 and 2 that it is not uncommon to connect the leading end, considered in regard to the direction of feed of the material to the kiln, of one chain to a particular clevis at a certain location on a specific rib 12, and also connect the trailing end of another chain, for example, to the same clevis, thereby minimizing connecting facilities. Further, sometimes the catenaries extend only in a longitudinal direction within the kilns and, during the rotation thereof, the various portions of the catenary configurations of chains will tumble and rub against each other to facilitate the removal of accumulated material therefrom. When such catenaries are slumped or collapsed against the lower surface of the kiln during the rotation thereof for example, especially those which are near the entrance end of the kiln which is receiving slurry or a wet mixture of material to be dried or calcined, the chains will become coated to various degrees with such slurry or wet material and then, during the continuous rotation of the kiln, the catenaries of chain will again become suspended and thereby efficiently transfer heat to the material adhering thereto as well as subjecting the material to ambient heat within the kiln, whereby drying, calcining, or other heat treatment of the material is effected in accordance with well known principles.

While the slumping and rubbing of coengaging lengths of the chains 14 against each other results in knocking a certain amount of the adhering material from the chains during the revolution of the kiln, an additional amount of material is dislodged from the links by the movement or rubbing of connected adjacent links with each other. Obviously, conventional elliptical link-type chain affords a minimum amount of removal from this source however and, in addition, such chain has the disadvantage of localized wear points rather than distributing the wear continuously around the entire length of the links as is possible when using rings or circular-type links. Any other projections or abutments on the links which will prevent continuous circular migration of each link with respect to its adjacent link likewise will result in localized wear and thereby provide a disadvantage.

In accordance with the stated objectives of the present invention, it is the principal purpose of the present invention to minimize the weight of the links employed in chains embodying the present invention as compared with corresponding links of comparable size but formed from cylindrical wire or rod stock, without substantially decreasing the heat-transferring exterior surface of each link, thereby resulting in conservation of power required to rotate the very heavy kilns within which such chains are employed. An additional advantage comprises the saving in material from which the chains are formed in that the preferred material is steel of one kind or another, details of which are set forth hereinafter, and the current prices of steel render such objective highly desirable. Stated another way, in comparing the present invention with conventional kiln chains presently used, weight for weight, either per link or per unit length of chain, the total heat transfer surface afforded by each link or each unit length of chain embodying the present invention is substantially greater than that afforded by each link or unit length of chain embodying conventional links and especially those formed from cylindrical Wire or rod stock.

To achieve the above-stated objective of the invention, the preferred configuration of link 16 is illustrated in FIGS. 38. It will be seen that such link is preferably circular but it is to be understood that certain of the advantages afforded by other aspects of the shape of the link, to be described, may be employed in links of other configurations such as elliptical or otherwise. However, a circular link offers the decided advantage of continuously repositioning the wear point engagement with adjacent links and hence, for maximum efficiency, the present invention preferably contemplates using circular links.

Further to minimize the wear caused by interengagement of adjacent, connected links, the inner surface 18 of the link, especially as seen in section in FIG. 4, is convex but is substantially of a flatter nature than the corresponding inner surface of a link 20, see FIG. 8, of similar thickness in the direction transverse to the plane of the link, formed from conventional cylindrical wire or rod stock. Preferably, said inner surface 18 has a radius which is substantially equal to but not greater than onehalf the inner diameter of the link 16.

As aresult of the above-described type of inner surface 18 on each link, and by referring to FIGS. 5 and 6, it will be seen that the coengaging inner surfaces 18 on adjacent links will be substantially coextensive for an appreciable portion of the width of said inner surfaces, thereby extending the coengaging surfaces of the two links to a far greater extent than occurs when even two circular links formed from conventional cylindrical wire or rod stock coengage each other.

By reference to FIG. 4 particularly, it also will be seen that, in the preferred construction of the links 16, the inner diameter, I.D., of the link 16 is at least three times as great as the radial thickness T of the links.

The primary means by which the overall weight of the links 16 is reduced over comparable sizes of links formed from conventional cylindrical wire or rod stock, while not sacrificing total exterior heat-transferring surface, is by providing at least one and preferably two similar annular concave surfaces 22 which extend inward from the opposite sides of each of the links 16, thereby producing a generally triangular cross-sectional configuration readily apparent from FIGS. 3, 5, 6 and 8, the inner surface 18 comprising the base of the triangle and the angular corners of the triangle being rounded. Further, especially by referring to FIG. 8, it will be seen that in the generally triangular cross-sectional configuration of the links 16, the radial thickness T of the links, or height of the trian gle, is somewhat less than the axial width or thickness W of the links, or base of the triangle.

Viewed differently, particularly in regard to the weightdecreasing aspect of the links of the present invention without sacrificing tot-a1 exterior heat-exchange surface areas, the links 16 might be considered as comprising a circular band B, see FIG. 8, which is relatively fiat in an axial direction to afford an advantageously relatively wide wear-distributing inner surface 18 of an arcu-ate nature. However, if a chain composed simply of such bands were provided, and depending upon the tensile forces sustained by 'a suspended chain, it is conceivable that the links would :become distorted to somewhat elliptical con-figuration, thereby no longer possessing the aforementioned advantages of circular links. To prevent this from occurring, it readily can be visualized that the circular band portions B of the link are reinforced by a bracing rib R, shown in FIG. 8, which is integral with and projects radially outward from the band B. In the other figures, this reinforcing rib is designated by the numeral 24. In the preferred construction of said rib 24, by reference to FIG. 8 particularly, it will be seen that the width or thickness t thereof is greater than the radial height h of the rib. Further, the peripheral edges of the band -B of the outer periphery of the reinforcing rib R are rounded.

Links embodying the present invention may be formed from a rather wide variety of steel such as alloy steels, including stainless, various types of carbon steel, and substantially any other type of steel having a controlled analysis and which, preferably, is heat-resistant. To

enhance the wear-resistance of the links, they are preferably suitably heat-treated, where applicable, so as to case harden or otherwise render the surfaces more resistant to wear, one variety of such treatment being known as carburizing. The preferred cross-sectional configuration of the links, especially as described above with respect to FIG. 8, is well suited to render the links capable of being treated to improve the wearing qualities thereof, as re fe-rred to above, without subjecting the links to any deleterious consequences during the use thereof, such as by chipping, flaking, or otherwise to any appreciable extent.

The links 16 preferably are formed from wire or bar stock which has been rolled to provide the desired crosssectional configuration and particularly the preferred configuration shown in detail in FIG. 8, or reasonable variations thereof. The links are suitably shaped from similar sections of the same length of such stock. Connection of the successive links may be accomplished in several ways. One of these is to form a stock of completed links which are either suitably butt-welded or otherwise connected such 'as by fire or forge welding. Although such welding may be accomplished by electrical resistance means, it has been found that fire or forge welding generally is superior for connecting the links of chain to be used as kiln chain.

After a supply of such links are produced, they may be connected by forge or fire welding connecting rings or links between pairs of pre-formed rings or links. In accordance with new techniques now available, connecting links or rings may be formed by a somewhat continuous casting procedure to connect pairs of said preformed links. If desired, all of the links may be cast from suitable steel, some being individually cast to form a supply, for example, to be connected by other rings or links cast therebetween subsequently.

To provide a more graphic presentation of the adv-antages of kiln chain links embodying the present invention over conventional kiln chain of several common types such .as those employing conventional elliptical links or circular rings, and both being formed from conventional cylindrical wire or rod stock, the following statistical data is submitted with reference to comparable links of two different types of standard chain and chain embodying the new configuration of ring-type links afforded by the present invention. One standard type of chain com-prises elliptical links formed from diameter wire having a minor inner diameter of 1%" and a major inner diameter of 2%". The second standard type of chain is formed from circular rings formed from diameter wire and having an inner diameter of 2 /2". These are contrasted with rings embodying the present invention in which the inner diameter is 3%", the outer diameter is 5", the radial thickness is and the thickness of the links in axial direction is 1%". Various data affording a comparison of weight to surface area ratios and the like are found in the following table:

Standard Standard New Elliptical Ring Ring Link Chain Chain Chain Wt. per it. of chain in lbs 6. O5 6. 72 7. 55 Surface area in sq. ft. per ft. of chain .75 .843 1.12 Surface area in sq. ft. per lb. of cl1ain .1245 148 different types of conventional kiln chain formed from cylindrical wire or rod stock.

It also will be seen from the recited details of the present invention that chain formed from links, preferably of a circular configuration, embodying the present invention, affords a far lower rate of wear between the links by distribution of the wear-contacting engagement over wider areas than conventional links, self-cleansing of the links in a far more efficient manner is provided over conventional links due to the great area of the coengaging surfaces between the links and the circular configuration thereof so as to promote continual gradual rotation of each link about its own axis, substantial economy resulting from the saving in metal in forming the links is afforded, and less power is consumed to operate kilns embodying such chains without sacrifice of total auxiliary heat-exchanging surface afforded by the chains, and the links may be formed and fabricated at least substantially as economically as conventional links.

One further possible advantage resides in the fact that if the present invention is employed in links of a somewhat larger diameter or overall size than conventional circular rings of elliptical links made from conventional cylindrical Wire or rod stock, fewer wear contacts points or areas per unit length of chain will be provided than that found in conventional chain using links of smaller diameter or overall size but formed from stock of comparable cross-sectional areas.

While the invention has been described and illustrated in its preferred embodiment, it should be understood that the invention is not to be limited to the precise details herein illustrated and described since the same may be carried out in other ways falling within the scope of the invention as claimed.

1 claim:

1. Chain for rotary kilns and the like com-prising connected substantially circular link-s having a uniform cross-sectional shape throughout the circumference thereof and a smooth arcuate inner surface wider in a direction transverse to the planes of the links than the thickness thereof within said planes thereof to distribute the wearing engagement with the links connected thereto and thereby minimize wear from the engagement between said links while affording greater wiping contact between said links for self-cleaning thereof from material adhering thereto than provided by links of comparable weight formed from substantially cylindrical Wire or rod stock.

2. The chain set forth in claim 1 further characterized by the transverse radius of the inner surface of said links being substantially equal to but no greater than half the inner diameter of said links.

3. Chain for rotary kilns and the like comprising connected substantially circular links having a uniform crosssectional shape throughout the circumference thereof and deformed from circular cross-section to provide substantially greater surface area than conventional links of similar weight made from cylindrical wire or rod stock, said deformed cross-section extending smoothly around the entire circumference of the links to enhance rotation of the links about their axes and thereby facilitate self-cleaning of said links.

4. Chain for rotary kilns and the like comprising connected links substantially circular within the planes thereof having continuous convex inner surfaces coengageable with each other and at least one continuous concave annular surface adjacent the outer surfaces of said links to provide thereon a substantially equal exterior surface but such links having less weight than a conventional :link of similar inner and outer diameter formed from cylindrical wire or rod stock.

5. The chain set forth in claim 4 further characterized by each link having a plurality of said continuous annular concave surfaces respectively extending inward from the opposite sides of the outer surfaces of said links to provide substantial reduction in weight with no decrease in exterior surface compared with said conventional links.

6. The chain set forth in claim 5 further characterized by said annular concave surfaces extending inward substantially equally from the opposite side surfaces of the outer surfaces of said links to provide a generally triangular cross-sectional shape for said links and the inner surface of said links comprising the base of said triangular shape.

7. The chain set forth in claim 6 further characterized by the corners of said triangular cross-sectional shape of said links being rounded.

8. The chain set forth in claim 5 further characterized by said convex inner surfaces having a radius substantially equal to but no greater than half the inner diameter of said links.

9. The chain set forth in claim 8 further characterized by said links being of greater thickness transversely to the plane thereof than along the radii of the links.

10. Chain for rotary kilns and the like comprising connected links substantially circular within the planes thereof and the inner surface portions of said links being convex and wider in a direction transverse to the plane of said links than the thickness of said links radially, whereby said links are deformed from a circular cross-sectional shape to decrease the weight thereof substantially while providing smooth exterior surfaces in a circumerential direction and the exterior area of said links being at least substantially equal to that of links of similar diameter made from cylindrical wire or rod stock of similar material.

11. The chain set forth in claim 10 further charac terized by the outer surface portion of said links including annular concavities which are smooth cincumfentially.

12. Chain for rotary kilns and the like comprising similar links connected together and each link comprising a substantially circular band forming the inner portion of each link and an annular bracing rib integral with and extending radially outward from said band to resist deformation from the circular shape of said links when the chain is subjected to tension, thereby providing links having a substantially greater ratio of exterior surface to weight than links of similar size formed from conventional cylindrical wire or rod stock.

13. The chain set forth in claim 12 further characterized by the innermost surface of said band being convex and wider than the radial dimension of said link through the bracing rib.

14. The chain set forth in claim 13 further characterized by said convex innermost surface of each link having a radius substantially equal to but not greater than half the inner diameter of said link.

15. The claim set forth in claim 14 further characterized by the peripheral edges of said band and periphery of said bracing rib being rounded and the height of said rib being less than the thickness thereof.

References Cited by the Examiner UNITED STATES PATENTS 1,910,873 5/1933 Zahn 263-33 2,001,227 5/1935 Vogel-Jorgensen 267-33 3,135,504 6/1964 Chisler 263-33 FOREIGN PATENTS 457,813 7/1913 France.

FREDERICK L. MATTESON, JR., Primary Examiner.

JOHN J. CAMBY, Exa'miner. 

1. CHAIN FOR ROTARY KILNS AND THE LIKE COMPRISING CONNECTED SUBSTANTIALLY CIRCULAR LINKS HAVING A UNIFORM CROSS-SECTIONAL SHAPE THROUGHOUT THE CIRCUMFERENCE THEREOF AND A SMOOTH ARCUATE INNER SURFACE WIDER IN A DIRECTION TRANSVERSE TO THE PLANES OF THE LINKS THAN THE THICKNESS THEREOF WITHIN SAID PLANES THEREOF TO DISTRIBUTE THE WEARING ENGAGEMENT WITH THE LINKS CONNECTED THERETO AND THEREBY MINIMIZE WEAR FROM THE ENGAGEMENT BETWEEN SAID LINKS WHILE AFFORDING GREATER WIPING CONTACT BETWEEN SAID LINKS FOR SELF-CLEANING THEREOF FROM MATERIAL ADHERING THERETO THAN PROVIDED BY LINKS OF COMPARABLE WEIGHT FORMED FROM SUBSTANTIALLY CYLINDRICAL WIRE OR ROD STOCK. 